1. Field of the Invention
This invention relates to storage interface. In particular, the invention relates to interface to Advanced Technology Attachment (ATA) drives.
2. Description of Related Art
The parallel ATA interface has existed in substantially the same form since 1989, and has become the highest volume disk drive interface in production. However, as demand for higher transfer and storage bandwidths increases, the parallel ATA is nearing its performance limit. Serial ATA interface is introduced to replace parallel ATA. The benefits of serial ATA include high data transfer rates up to 150 MB/s (compared to 100 MB/s for parallel ATA), low cost, easy installation and configuration, low pin count, etc. However, due the large amount of parallel ATA currently in existence, the transition from parallel ATA to serial ATA may be a problem.
Parallel ATA allows up to two devices to be connected to a single port using a master/slave communication technique. One ATA device is configured as a master and the other slave. Both devices are daisy-chained together via one ribbon cable that is an unterminated multidrop bus. This bus or connection is typically referred to as a parallel channel. In addition, a personal computer (PC) may have two parallel ATA channels: a primary channel and a secondary channel.
Serial ATA, on the other hand, connects each of the two drives with individual cables in a point-to-point fashion. Software drivers for parallel ATA have to be modified to accommodate serial ATA. In addition, new serial ATA interface is preferably backward compatible with parallel ATA device drivers to avoid transition costs and provide an easy migration path.
Therefore, there is a need to have an efficient technique to emulate parallel ATA interface in a serial ATA environment.